Combustion engines now in use operate with adiabatic expansion of a gas. This means that the gas has an initially high pressure and an initially high temperature, and that it has a finally low pressure and a finally low temperature. The efficiency of the engine and the power output of the engine increase with increasing temperature difference between the initial state and the final state. At the final state the gas is exhausted into the environment. There is nothing one can do to reduce the pressure and/or the temperature of the final state. The effort toward more power and higher efficiency has therefore been directed toward raising the initial pressure and temperature. It is therefore necessary to cool the engine. Generally speaking 1/3 of the combustion energy of the fuel goes to useful power, 1/3 is lost by cooling and 1/3 is lost with the exhaust.